Some vibratory compactors are manufactured with an option of varying the amplitude and frequency of drum vibrations. The amplitude of the vibrations is changed through rotating of a mechanical wheel on the side of a drum. Rotating such a mechanical wheel would change the spacing between eccentric masses on an eccentric shaft inside the drum. The more the masses are aligned on one side of the shaft, the greater an impact force is applied onto the ground and the greater the amplitude of the drum. The more the eccentric masses are symmetrically distributed around the shaft, the less the impact force is applied onto the ground. Usually, the frequency and amplitude are set in pairs to produce a specific amount of force. The produced force is known as an eccentric or centrifugal force that is applied to a surface during compaction. The centrifugal force generated by the rotation of an eccentric weight in the drum of the compactor can be expressed as:Fec=mecrecωec2 sin(ωect)=A sin(2πft)
where mecrec is the moment of the eccentric mass, ωec is the angular frequency of rotation, A is the amplitude, and f is the frequency.
There is a strong desire from the market for a means for allowing a vibratory roller to change the amplitude while the compaction machine is operating. However, in order to use two eccentric shaft systems (inner and outer eccentric shafts that move relative to each other to change the amplitude), an operator should get off the compaction machine and manually change the amplitude if more than two amplitude settings are desired. As a result, this inconvenience causes inefficiency and there is a necessity for finding a new way to adjust and manage the variable amplitude setting.